JP2015179042A - current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor capable of suppressing a size increase while magnifying a bias magnetic field.SOLUTION: A current sensor comprises: a magnetoelectric transducer (10); a bias magnet (20); and a magnetic shield (30). The magnetic shield (30), the bias magnet (20), and the magnetoelectric transducer (10) are aligned in a height direction orthogonal to a flow direction of a measurement target current, and the bias magnet (20) includes a first N pole (21) and a first S pole (22) whose magnetization directions are aligned in the height direction, and a second S pole (23) and a second N pole (24) whose magnetization directions are aligned in the height direction. The first N pole (21) is adjacent to the second S pole (23) and the first S pole (22) is adjacent to the second N pole (21) in the flow direction, whereby a bias magnetic field forms a closed magnetic circuit. Bottom surfaces (21a, 23a) of the first N pole (21) and the second S pole (23) are adhesively bonded to the magnetic shield (30) and bottom surfaces (22a, 24a) of the first S pole (22) and the second N pole (24) face the magnetoelectric transducer (10).

Description

  The present invention relates to a current sensor including a magnetoelectric conversion element that converts a magnetic field to be measured into an electrical signal, a bias magnet that transmits a bias magnetic field to the magnetoelectric conversion element, and a magnetic shield that suppresses transmission of an external magnetic field to the magnetoelectric conversion element. It is about.

  As shown in Patent Document 1, a current sensor in which a magnetoelectric conversion element is formed on a sensor substrate and the sensor substrate is surrounded by a magnetic shield is known as a prior art. A bias magnet for applying a bias magnetic field is provided in the magnetic shield, and an initial value of the magnetoelectric conversion element is determined by the bias magnetic field.

JP 2013-11469 A

  As described above, in the current sensor disclosed in Patent Document 1, the initial value of the magnetoelectric conversion element is determined by the bias magnetic field. When the strength of the bias magnetic field is increased, the size of the bias magnet is increased, which may increase the size of the current sensor.

  In view of the above problems, an object of the present invention is to provide a current sensor in which an increase in physique is suppressed while a bias magnetic field is amplified.

  In order to achieve the above-described object, the present invention provides a magnetoelectric conversion element (10) for converting a magnetic field to be measured generated by the flow of the current to be measured into an electric signal, and a bias magnet (20) for allowing the magnetoelectric conversion element to transmit a bias magnetic field. And a magnetic shield (30) made of a magnetic material that suppresses transmission of an external magnetic field different from each of the magnetic field to be measured and the bias magnetic field through the magnetoelectric transducer, and the magnetic shield, the bias magnet, and the magnetoelectric Each of the conversion elements is arranged in a height direction orthogonal to the flow direction of the current to be measured, and the bias magnet includes a first N pole (21), a first S pole (22), and a high magnetization direction along the height direction. It has the 2nd S pole (23) and the 2nd N pole (24) which a magnetization direction follows along a direction, the 1st N pole and the 2nd S pole adjoin in the flow direction, and the 1st S pole and the 2nd N pole adjoin By The bias magnetic field forms a closed magnetic circuit, the bottom surfaces (21a, 23a) of the first N pole and the second S pole are bonded to the magnetic shield, and the bottom surfaces (22a, 24a) of the first S pole and the second N pole are magnetoelectric. It is characterized by facing the conversion element.

  Thus, according to the present invention, the magnetization direction of the bias magnet (20) is along the height direction, and the bottom surfaces (21a, 23a) perpendicular to the magnetization direction are bonded to the magnetic shield (30). According to this, the bias magnetic field is collected by the magnetic shield (30), and a part of the magnetic shield (30) functions as the bias magnet (20) (magnet collection yoke). Therefore, the length in the height direction of the bias magnet (20) becomes pseudo thick, and the bias magnetic field is amplified. Thus, the bias magnetic field is amplified without increasing the size of the bias magnet (20) (current sensor (100)).

  The magnetic shield has a flat plate-shaped first shield (31) and a second shield (32) whose main surfaces are orthogonal to the height direction, and the first shield and the second shield are arranged in the height direction, and between them. A bias magnet, a magnetoelectric conversion element, and a measured conductor through which a current to be measured flows are provided in the space, and the bias magnet is a first main that faces the second shield among the two main surfaces of the first shield. It is provided on the surface (31a).

  According to this, as compared with the configuration in which the magnetic shield (30) has a cylindrical shape, the magnetic field distribution of the bias magnetic field is suppressed from being distorted by the magnetic shield (30). Therefore, it is easy to design a magnetic field that passes through the magnetoelectric transducer (10).

  The magnetoelectric conversion element transmits the magnetic field component along the flow direction in the bias magnetic field and the magnetic field component along the horizontal direction perpendicular to the height direction and the flow direction in the magnetic field to be measured. And only a magnetic field along a prescribed plane defined by the horizontal direction.

  As described above, the magnetic shield (30) has a flat plate shape with the main surface along the height direction. Therefore, when an external magnetic field orthogonal to the height direction attempts to pass through the current sensor (100), the external magnetic field is bent due to the magnetic shield (30) and is prevented from passing through the magnetoelectric transducer (10). The However, when the external magnetic field is along the height direction, the external magnetic field passes through the magnetic shield (30) without being bent, and thus passes through the magnetoelectric transducer (10). On the other hand, the magnetoelectric transducer (10) detects only a magnetic field along a defined plane orthogonal to the height direction. Therefore, even if the external magnetic field along the height direction passes through the magnetoelectric conversion element (10) via the magnetic shield (30), it is suppressed that the detection accuracy of the magnetic field to be measured is lowered. Since the magnetic shield (30) has a simple flat plate shape as described above, the magnetic shield (30) can be easily manufactured.

  In addition, although the elements described in the claims and the means for solving the problems are attached with parentheses, the parentheses are attached to each component described in the embodiment. This is to simply show the correspondence with the elements, and does not necessarily indicate the elements themselves described in the embodiments. The description of the reference numerals with parentheses does not unnecessarily narrow the scope of the claims.

It is sectional drawing which shows schematic structure of a current sensor. It is a schematic diagram for demonstrating the magnetic field which permeate | transmits a magnetoelectric conversion element. It is sectional drawing for demonstrating that a part of magnetic shield functions as a bias magnet. It is sectional drawing which shows the modification of a current sensor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The current sensor according to the present embodiment will be described with reference to FIGS. Hereinafter, the three directions orthogonal to each other are referred to as an x direction, a y direction, and a z direction. A plane defined by the x direction and the y direction is referred to as a defined plane. The x direction corresponds to the lateral direction described in the claims, the y direction corresponds to the flow direction described in the claims, and the z direction corresponds to the height direction described in the claims.

  The current sensor 100 includes the magnetoelectric conversion element 10, the bias magnet 20, and the magnetic shield 30, and detects a measured current flowing through the measured conductor 90. The magnetoelectric transducer 10 transmits a bias magnetic field generated from the bias magnet 20 and a measured magnetic field generated by the flow of the measured current. Therefore, the magnetoelectric conversion element 10 generates an electrical signal corresponding to the combined magnetic field composed of the bias magnetic field and the measured magnetic field.

  As shown in FIG. 1, each of the magnetoelectric conversion element 10, the bias magnet 20, and the magnetic shield 30 is arranged in the z direction, and the magnetic field that is different from each of the measured magnetic field and the bias magnetic field is generated by the magnetic shield 30. 10 is suppressed. The bias magnet 20 is bonded to the magnetic shield 30, thereby amplifying the bias magnetic field.

  The current sensor 100 according to the present embodiment includes a calculation unit 40, a support substrate 50, and a fixing unit 60 in addition to the above-described components. The calculation unit 40 calculates a current to be measured based on the electrical signal output from the magnetoelectric conversion element 10 and is mounted on the support substrate 50 together with the magnetoelectric conversion element 10. The support substrate 50 is obtained by forming a wiring pattern on an insulating substrate, and not only mounts the magnetoelectric conversion element 10 and the calculation unit 40 but also electrically connects them. As shown in FIG. 1, the support substrate 50 is mounted on the conductor to be measured 90, and the magnetoelectric conversion element 10 and the calculation unit 40 are mounted on the back surface 50b of the mounting surface 50a. The fixed portion 60 is made of a non-conductive and non-magnetic resin material. The fixing unit 60 fixes the support substrate 50 on which the magnetoelectric transducer 10 and the calculation unit 40 are mounted, and the magnetic shield 30 to which the bias magnet 20 is bonded, to the conductor 90 to be measured.

  The above is the schematic configuration of the current sensor 100. Hereinafter, mainly the magnetoelectric transducer 10, the bias magnet 20, and the magnetic shield 30 will be described in detail, and then the effects of the current sensor 100 will be described.

  The magnetoelectric conversion element 10 converts a magnetic field transmitted through itself into an electric signal. As shown in FIG. 1, since the measured current flows in the y direction, a measured magnetic field is generated around it. The bias magnet 20 forms a closed magnetic circuit around the x direction, and the magnetoelectric transducer 10 is positioned between the bias magnet 20 and the conductor to be measured 90 in the z direction. Therefore, as shown in FIG. 2, a magnetic field component along the x direction in the magnetic field to be measured is transmitted to the magnetoelectric conversion element 10, and a magnetic field component along the y direction in the bias magnet 20 is transmitted. As described above, since the composite magnetic field is composed of the bias magnetic field and the magnetic field to be measured, when the magnetic field to be measured is zero, the composite magnetic field is equal to the bias magnetic field. Therefore, the angle θ formed by the combined magnetic field and the bias magnetic field on the specified plane orthogonal to the z direction is zero when the measured magnetic field is zero, but when the measured magnetic field is finite, the angle θ is also finite. Thus, the value of the angle θ varies depending on the strength of the magnetic field to be measured.

  The magnetoelectric conversion element 10 detects only the magnetic field along the specified plane. Although not shown, the magnetoelectric conversion element 10 has a pinned layer with a fixed magnetization direction, a free layer with a fixed magnetization direction, and a nonmagnetic intermediate layer provided between them. This is a magnetoresistive effect element whose resistance value is determined by the angle formed by the magnetization direction. The magnetization direction of the pinned layer is along a prescribed plane, and the magnetization direction of the free layer is determined by a magnetic field along the prescribed plane. As described above, the combined magnetic field is transmitted through the magnetoelectric transducer 10. Therefore, the magnetization direction of the free layer is determined by the direction of the combined magnetic field (angle θ), and the resistance value is also determined. As described above, since the angle θ depends on the magnetic field to be measured, the resistance value of the magnetoelectric transducer 10 also depends on the angle θ. Although not shown, a bridge circuit is formed by connecting a plurality of magnetoelectric transducers 10 in series from a power source at a midpoint, and the midpoint potential is output to the calculation unit 40 as an electrical signal of the magnetoelectric transducer 10. The Therefore, the electrical signal of the magnetoelectric transducer 10 also depends on the angle θ. The calculation unit 40 stores a correlation between the electrical signal of the magnetoelectric transducer 10 and the angle θ, and a correlation between the angle θ and the measured magnetic field (measured current). The calculation unit 40 calculates the current to be measured based on the correlation and the electric signal of the magnetoelectric conversion element 10.

  The bias magnet 20 transmits the bias magnetic field to the magnetoelectric conversion element 10. The bias magnet 20 has a first N pole 21 and a first S pole 22 whose magnetization directions are in the z direction, and a second S pole 23 and a second N pole 24 whose magnetization directions are in the z direction. In the y direction, the first N pole 21 and the second S pole 23 are adjacent to each other, and the first S pole 22 and the second N pole 24 are adjacent to each other. As a result, the bias magnetic field forms a closed magnetic circuit. As shown in FIG. 3, the bottom surfaces 21 a and 23 a of the first N pole 21 and the second S pole 23 are bonded to the magnetic shield 30, and the bottom surfaces 22 a and 24 a of the first S pole 22 and the second N pole 24 are connected to the magnetoelectric transducer 10. Opposite. More specifically, each of the bottom surfaces 21a and 23a is bonded to a first main surface 31a of a first shield 31 described later via an adhesive (not shown), and each of the bottom surfaces 22a and 24a is connected via a fixing portion 60. It faces the magnetoelectric transducer 10.

  The magnetic shield 30 prevents an external magnetic field from passing through the magnetoelectric conversion element 10. The magnetic shield 30 has shields 31 and 32 made of a magnetic material. Each of the shields 31 and 32 has a flat plate shape in which the main surface having the largest area is orthogonal to the z direction. The shields 31 and 32 are arranged in the z direction, and a support substrate 50 on which the magnetoelectric conversion element 10 and the bias magnet 20 are mounted and a conductor to be measured 90 are provided in the space between them. As shown in FIG. 1, the first main surface 31a of the first shield 31 and the first main surface 32a of the second shield 32 face each other in the z direction, and the bias magnet 20 is provided on the first main surface 31a. ing.

  Next, the function and effect of the current sensor 100 according to this embodiment will be described. As shown by the double-ended arrows in FIG. 3, the first N pole 21 and the first S pole 22, and the second S pole 23 and the second N pole 24 have the magnetization directions along the z direction and perpendicular to the magnetization directions, respectively. The bottom surfaces 21 a and 23 a of the second S poles 23 are bonded to the magnetic shield 30. According to this, the bias magnetic field is collected by the magnetic shield 30 (first shield 31), and a part of the magnetic shield 30 functions as the bias magnet 20 (magnet collection yoke). Therefore, as indicated by a broken line in FIG. 3, the length of the bias magnet 20 in the z direction becomes pseudo thick, and the bias magnetic field is amplified. Thus, in the case of the current sensor 100 according to the present embodiment, the bias magnetic field is amplified without increasing the size of the bias magnet 20 (current sensor 100).

  The magnetic shield 30 has flat shields 31 and 32 whose main surfaces are orthogonal to the z direction, and the bias magnet 20 is provided on the first main surface 31 a of the first shield 31. According to this, as compared with the configuration in which the magnetic shield has a cylindrical shape, the magnetic field distribution of the bias magnetic field is suppressed from being distorted by the magnetic shield 30. Therefore, the design of the magnetic field that passes through the magnetoelectric transducer 10 is facilitated.

  The magnetoelectric transducer 10 transmits a magnetic field component along the x direction in the magnetic field to be measured and a magnetic field component along the y direction in the bias magnet 20. The magnetoelectric transducer 10 detects only a magnetic field along a specified plane orthogonal to the z direction.

  As described above, the shields 31 and 32 have a flat plate shape whose main surface is along the height direction. Therefore, as shown by a white arrow in FIG. 1, when an external magnetic field orthogonal to the z direction attempts to pass through the current sensor 100, the external magnetic field is bent for the magnetic shield 30 and passes through the magnetoelectric transducer 10. It is suppressed. However, when the external magnetic field is along the z direction, the external magnetic field is transmitted without being bent by the magnetic shield 30, and thus is transmitted through the magnetoelectric transducer 10. On the other hand, the magnetoelectric transducer 10 detects only a magnetic field along a prescribed plane orthogonal to the z direction. Therefore, even if the external magnetic field along the z direction passes through the magnetoelectric conversion element 10 via the magnetic shield 30, it is possible to suppress a decrease in the detection accuracy of the magnetic field to be measured. Since the magnetic shield 30 adopts a simple flat plate shape as described above, the magnetic shield 30 can be easily manufactured.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  An example in which the current sensor 100 according to the present embodiment includes the calculation unit 40, the support substrate 50, and the fixing unit 60 has been shown. However, the current sensor 100 may have at least one of these, or may not have one.

  The magnetoelectric conversion element 10 according to the present embodiment shows an example in which only a magnetic field along a prescribed plane is detected. However, when the magnetic shield 30 has a shape that suppresses transmission of an external magnetic field along the z direction through the magnetoelectric conversion element 10, the magnetoelectric conversion element 10 may detect not only the prescribed plane but also a magnetic field along the z direction.

  An example in which the magnetoelectric conversion element 10 according to the present embodiment is a magnetoresistive effect element having a pinned layer, a free layer, and an intermediate layer is shown. However, the magnetoelectric conversion element 10 is not limited to the above example, and for example, an anisotropic magnetoresistive element (AMR) or a Hall element can be adopted. When the intermediate layer has conductivity, the magnetoelectric conversion element 10 is a giant magnetoresistance effect element (GMR), and when the intermediate layer has insulation, the magnetoelectric conversion element 10 is a tunnel magnetoresistance effect element (TMR). .

  The calculation unit 40 according to the present embodiment shows an example in which the correlation between the electrical signal of the magnetoelectric conversion element 10 and the angle θ and the correlation between the angle θ and the measured magnetic field (measured current) are stored. . However, the calculation unit 40 may store a correlation between the electrical signal of the magnetoelectric transducer 10 and the current to be measured. In short, the calculation unit 40 only needs to have data necessary for calculating the current to be measured based on the electrical signal of the magnetoelectric transducer 10.

  In the present embodiment, the bottom surfaces 21 a and 23 a of the first N pole 21 and the second S pole 23 are bonded to the first main surface 31 a of the first shield 31, and the bottom surfaces 22 a and 24 a of the first S pole 22 and the second N pole 24 are formed. The example facing the magnetoelectric conversion element 10 was shown. However, as shown in FIG. 4, in the configuration in which the positions of the first shield 31 and the second shield 32 are interchanged, the bottom surfaces 22 a and 24 a of the first S pole 22 and the second N pole 24 respectively connect the conductor 90 to be measured and the support substrate 50. Thus, a configuration that indirectly faces the magnetoelectric conversion element 10 may be employed.

DESCRIPTION OF SYMBOLS 10 ... Magnetoelectric conversion element, 20 ... Bias magnet, 21 ... 1st N pole, 21a ... Bottom surface, 22 ... 1st S pole, 22a ... Bottom surface, 23 ... 2nd S pole , 23a ... bottom surface, 24 ... second N pole, 24a ... bottom surface, 30 ... magnetic shield, 100 ... current sensor

Claims (7)

A magnetoelectric transducer (10) for converting a magnetic field to be measured generated by the flow of the current to be measured into an electrical signal;
A bias magnet (20) that transmits a bias magnetic field to the magnetoelectric transducer;
A magnetic shield (30) made of a magnetic material that suppresses transmission of an external magnetic field different from each of the magnetic field to be measured and the bias magnetic field through the magnetoelectric transducer, and
Each of the magnetic shield, the bias magnet, and the magnetoelectric transducer is arranged in a height direction orthogonal to the flow direction of the current to be measured,
The bias magnet includes a first N pole (21) and a first S pole (22) whose magnetization direction extends along the height direction, and a second S pole (23) and a second N pole (which extends along the height direction). 24), the first N pole and the second S pole are adjacent to each other in the flow direction, and the first S pole and the second N pole are adjacent to each other, so that the bias magnetic field forms a closed magnetic circuit. And
The bottom surfaces (21a, 23a) of the first N pole and the second S pole are bonded to the magnetic shield, and the bottom surfaces (22a, 24a) of the first S pole and the second N pole are opposed to the magnetoelectric transducer. A current sensor. The magnetic shield has a flat plate-shaped first shield (31) and a second shield (32) whose main surfaces are orthogonal to the height direction,
Each of the first shield and the second shield is arranged in the height direction, and the bias magnet, the magnetoelectric conversion element, and the measured conductor through which the measured current flows are provided in the space therebetween,
2. The current sensor according to claim 1, wherein the bias magnet is provided on a first main surface (31 a) facing the second shield, of two main surfaces of the first shield. A magnetic field component along the flow direction in the bias magnetic field and a magnetic field component along a horizontal direction perpendicular to the height direction and the flow direction in the measured magnetic field are transmitted to the magnetoelectric transducer,
The current sensor according to claim 2, wherein the magnetoelectric conversion element detects only a magnetic field along a prescribed plane defined by the flow direction and the lateral direction. A support substrate (50) on which the magnetoelectric transducer is mounted;
The current sensor according to claim 2, wherein the support substrate is mounted on the conductor to be measured.   5. The current according to claim 4, wherein the bottom surfaces of the first S pole and the second N pole are indirectly opposed to the magnetoelectric conversion element through the conductor to be measured and the support substrate. Sensor. A calculation unit (40) for calculating the measured current based on an electric signal output from the magnetoelectric conversion element;
The current sensor according to claim 4, wherein the calculation unit is mounted on the support substrate. A fixing portion (60) made of a non-conductive and non-magnetic resin material;
The support substrate on which the magnetoelectric transducer and the calculation unit are mounted, and the magnetic shield to which the bias magnet is bonded are fixed to the conductor to be measured by the fixing unit. Item 7. The current sensor according to Item 6.

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